Presentation title: “The Acoustic Bubble”
Presenter: Prof. Timothy Leighton
Time: 14:30, May 28, 2018
Location: Conference Room 315 of the Underwater Acoustic Engineering Building
Short Bio of the presenter:
Timothy Leighton is Professor of Ultrasonics and Underwater Acoustics within the Institute of Sound and Vibration Research at the University of Southampton, UK. He is an Academician of three National Academies: the Royal Society, the Royal Academy of Engineering, and the Academy of Medical Sciences. He graduated in 1985 with a Double First Master of Arts (Physics and Theoretical Physics) and, in 1988, a PhD, both from the University of Cambridge. He has won 8 international medals, and 6 awards for invention. The citation of the 2006 Paterson Medal of the Institute of Physics states that “Timothy Leighton’s contribution is outstanding in both breadth and depth. His is an acknowledged world leader in four fields”. In 2017 the Royal Society announced its award to him of the Royal Society Clifford Paterson Medal, the citation being “for translation of his fundamental research into acoustics and its application in many areas including anti-microbial resistance, mine detection, foetal scanning, catastrophe relief, climate change and marine life”. He runs a research group, is the founding Chairman of NAMRIP (the Network for Anti-Microbial Resistance and Infection Prevention) and the founding Chairman of HEFUA (Health Effects of Ultrasound in Air). He advises numerous governmental and international bodies.
Abstract of the presentation:
Bubbles couple to sound fields to an extraordinary extent, generating and scattering sound, and changing the chemical, physical and biological environments around them when excited to pulsate by an appropriate sound field. This paper opens with the way that the sound emitted by bubbles, when they are injected into the ocean by breaking waves, helps track the >1 billion tonnes of atmospheric carbon that transfers between atmosphere and ocean annually. However, compared to carbon dioxide, atmospheric methane has at least 20 times the ability, per molecule, to generate ‘greenhouse’ warming. Worldwide there is more than twice the amount of carbon trapped in the seabed in the form of methane hydrate than the amount of carbon worldwide in all other known conventional fossil fuels. Acoustics can track the release of bubbles of seabed methane as this hydrate dissociates in response to increasing ocean temperatures, an effect cited by some as a possible climate apocalypse.
However the ones with most experience of directing sound fields at bubbly ocean water in order to exploit the interaction between underwater sound and bubbles, are marine mammals. Having evolved over tens of millions of years to cope with the underwater acoustic environment, the hypothesis is that cetaceans may have developed techniques from which we could learn. This paper outlines some of the possible interactions, focusing on the use of bubble nets by whales and dolphins to trap prey, and exploring the challenges and opportunities that whales and dolphins face when blowing bubble nets to obtain food.
